EP4094854A1

EP4094854A1 - Temper rolling method for cold-rolled steel sheet

Info

Publication number: EP4094854A1
Application number: EP20922979.8A
Authority: EP
Inventors: Kentaro Ishii; Ken Kurisu; Hiroshi Nishimura; Daisuke Tagawa; Masami Tsujimoto
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2020-03-05
Filing date: 2020-11-20
Publication date: 2022-11-30
Anticipated expiration: 2040-11-20
Also published as: WO2021176777A1; JPWO2021176777A1; EP4094854A4; CN115210009A; TWI766459B; EP4094854B1; TW202133958A; JP7063415B2; KR20220129627A

Abstract

The present invention provides a method for performing temper rolling on a cold rolled steel sheet, the method being designed to prevent the occurrence of problems such as jumping; the method relates to wet temper rolling and addresses changes in a concentration of a temper rolling liquid and changes in a load, and the method is applicable to both a rolling mill with a single stand and a rolling mill with multiple stands.

A method for performing temper rolling on a cold rolled steel sheet, the temper rolling including wet temper rolling, the cold rolled steel sheet being an annealed cold rolled steel sheet, the method including setting a tension T (kgf/mm²) per unit cross-sectional area of the steel sheet for the temper rolling, based on a carbon content C (mass%) of the cold rolled steel sheet.

Description

Technical Field

The present invention relates to a method for performing temper rolling on a cold rolled steel sheet and, in particular, relates to a method for setting a tension for wet temper rolling.

Background Art

Cold rolled steel sheets are manufactured by rolling a hot rolled steel sheet at room temperature to a required sheet thickness. The steel sheet undergoes work hardening in this process, and, therefore, in some instances, a step of annealing for softening is necessary. The step is followed by temper rolling. Purposes of temper rolling include elimination of yield point elongation, shape correction, adjustment of a surface roughness of the steel sheet, and adjustment of material properties.
Types of temper rolling processes include wet temper rolling, which uses a temper rolling liquid, and dry temper rolling, which uses no temper rolling liquid. In the related art, in particular, in the field of steel sheets for cans, dry temper rolling was predominantly employed from the standpoint of aesthetics. However, with an increase in demand for various specifications for the material properties of the steel sheet, the trend has shifted toward wet temper rolling, with which various material properties can be created by adjusting a property of a temper rolling liquid, thereby controlling an elongation ratio.
The adjustment of a surface roughness of the steel sheet, which is one of the purposes of the temper rolling, is carried out by transferring a surface roughness of work rolls to the steel sheet. For stable adjustment of the surface roughness of the steel sheet, the surface roughness of work rolls and a rolling load need to be uniquely determined with respect to the desired surface roughness of the steel sheet. On the other hand, the adjustment of the material properties is carried out by controlling parameters such as an elongation ratio for temper rolling, such that the parameters reach predetermined values. As stated, the surface roughness of work rolls and the rolling load are uniquely determined in accordance with the surface roughness of the steel sheet. As referred to herein, the elongation ratio is defined as a ratio of the difference between an entry-side sheet thickness and a delivery-side sheet thickness to the delivery-side sheet thickness. Accordingly, the adjustment of the elongation ratio is typically carried out by controlling tensions of the steel sheet, that is, tensions before the steel sheet enters a rolling mill and after the steel sheet exits the rolling mill, thereby controlling the entry-side sheet thickness and the delivery-side sheet thickness.
Regarding wet temper rolling, a phenomenon called jumping is known. The jumping is a so-called anomalous elongation, in which, when the elongation ratio is low, namely, less than or equal to 5%, the elongation ratio unstably changes. A problem with the occurrence of jumping is that the sheet thickness and material properties of the steel sheet significantly change.
Some methods for preventing jumping are as follows. Patent Literature 1 discloses a method in which a concentration of a temper rolling liquid is adjusted in accordance with a material property and the elongation ratio. Patent Literature 2 discloses a method in which wet temper rolling and dry temper rolling are used in combination in a rolling mill including multiple stands.

Citation List

Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2016-150353
PTL 2: Japanese Unexamined Patent Application Publication No. 2018-015801

Summary of Invention

Technical Problem

Unfortunately, the method described in Patent Literature 1 for preventing jumping by adjusting the concentration of a temper rolling liquid presents a problem in that preventing the occurrence of jumping exclusively and reliably is difficult because the difference in the concentration may cause a change in the proportion of the surface roughness pattern transferred from the work rolls to the steel sheet, which may result in changes in the surface roughness and an appearance of the steel sheet. Furthermore, the method described in Patent Literature 2, in which wet temper rolling and dry temper rolling are used in combination, poses a problem in that the method is not applicable to a rolling mill with a single stand.
An object of the present invention is to provide a method for performing temper rolling on a cold rolled steel sheet, the method being designed to prevent the occurrence of jumping; the method relates to wet temper rolling and addresses changes in a concentration of a temper rolling liquid and changes in a load, and the method is applicable to both a rolling mill with a single stand and a rolling mill with multiple stands.

Solution to Problem

As stated, the surface roughness of work rolls and the rolling load are uniquely determined in accordance with the desired surface roughness of the steel sheet. Performing temper rolling at a predetermined elongation ratio further requires appropriate setting of a tension. In instances where the tension setting is excessively high, the jumping, which is anomalous elongation, occurs. Furthermore, in instances where the tension setting is excessively low, an elongation ratio deficiency and/or a bellows-like shape defect, referred to as cross buckling, occur.
To solve the problems described above, the present inventors directed to the fact that mechanical properties of a steel sheet are strongly affected by a carbon content of the steel sheet and diligently performed studies regarding the relationship between the carbon content and jumping. As a result, it was discovered that the tension associated with temper rolling is related to the carbon content of the steel sheet, and, accordingly, a method for performing temper rolling on a cold rolled steel sheet that solves the problems was invented.
A summary of the present invention is as follows.

[1] A method for performing temper rolling on a cold rolled steel sheet, the temper rolling including wet temper rolling, the cold rolled steel sheet being an annealed cold rolled steel sheet, the method including setting a tension T (kgf/mm²) for the temper rolling based on a carbon content C (mass%) of the cold rolled steel sheet.
[2] The method for performing temper rolling on a cold rolled steel sheet according to [1], wherein the tension T is set based on a sheet thickness t (mm) of the cold rolled steel sheet, a load w (tonf/mm) per unit width, and a surface roughness a (µmRa) of a work roll, in addition to the carbon content C of the cold rolled steel sheet.
[3] The method for performing temper rolling on a cold rolled steel sheet according to [2], wherein the tension T is set based on formula (1) below,

\begin{array}{l} t \times w \times (- 200 \times a - 90) / (a \times (1 - logC)) + 17.1 \leq T \leq t \\ \times w \times (- 200 \times a + 10) / (a \times (1 - logC)) + 17.1 \end{array}

²

The present invention prevents the occurrence of jumping, an improper elongation ratio, and a bellows-like shape defect referred to as cross buckling, in wet temper rolling, even in instances in which there is a change in a concentration of a temper rolling liquid and/or there is a change in a load. Furthermore, the present invention is applicable to both a rolling mill with a single stand and a rolling mill with multiple stands.

Brief Description of Drawings

[Fig. 1] Fig. 1 is a schematic diagram of a temper rolling equipment, illustrating an embodiment of a method for performing temper rolling of the present invention. Description of Embodiments
The present invention will now be described in more detail.
An embodiment of the present invention will be described with reference to the drawing. Fig. 1 is a schematic diagram illustrating an embodiment, according to the present invention, of a method for performing temper rolling on a cold rolled steel sheet. Fig. 1 schematically illustrates a temper rolling equipment for performing temper rolling on a cold rolled steel sheet that has undergone an annealing treatment. The temper rolling equipment includes work rolls 1 and back-up rolls 2 for performing temper rolling. The work rolls 1 apply a thickness reducing force to a steel sheet 3 from above and below, and the back-up rolls 2 support the work rolls 1. The rolling is performed with a temper rolling liquid supplied through temper rolling liquid supply nozzles 5.
Tension meters (not illustrated) are installed in front of and behind the work rolls 1. The tension meters are used to measure a tension T (kgf/mm², a tension per unit cross-sectional area), which is a tension imparted to the steel sheet 3. The steel sheet 3 is reduced in thickness at a predetermined load by the upper and lower work rolls 1 and travels in a travel direction 4 in a state in which the steel sheet 3 has been imparted with a set tension. In this instance, if the tension setting is excessively high, jumping occurs because the elongation ratio unstably changes. If the tension setting is excessively low, an elongation ratio deficiency and cross buckling occur.
In the temper rolling, the tension T, which is set based on various factors (described below), is imparted by adjusting a rotational speed of the work rolls 1.
The present inventors conducted many experiments repeatedly to study various factors that affect the occurrence of the problems, among the rolling conditions of temper rolling, and discovered that the following factors are influential factors.
The specific factors are a sheet thickness t (mm) of the steel sheet, a load w (tonf/mm) per unit width, a surface roughness a (µmRa) of a work roll, a carbon content C (mass%) of the steel sheet, and a tension T (kgf/mm²) per unit cross-sectional area.
An investigation was made on the relationship between each of these factors and the occurrence of jumping, and it was discovered that for the sheet thickness t and the tension T, the greater the value, the more likely it is that jumping occurs. It was also discovered that for the surface roughness a of a work roll and the carbon content C, the smaller the value, the more likely it is that jumping occurs.
However, all of these factors, except for the tension T, are factors that are set within a specific range according to the specifications of the product steel sheet. Accordingly, the settings cannot be freely changed. That is, it was discovered that in instances where the tension T can be set to be an optimal value, with the factors other than the tension T being unchanged, the occurrence of jumping can be effectively inhibited.
Accordingly, studies were conducted on the manner by which the tension T can be set to be an optimal value.
As described above, in instances where the tension T is high, it is likely that jumping occurs, and in instances where the tension T is low, it is likely that a shape defect called cross buckling occurs. In temper rolling, there is a demand for setting the tension T at a large value so that a stable shape can be achieved, and, therefore, in association with the occurrence of jumping, it is important to determine the upper limit of the tension setting. Furthermore, it was concluded that the lower limit of the tension setting also needs to be set so that shape defects can be prevented, and, accordingly, various experiments were conducted. As a result, the following method for setting the tension T was derived.
In the present invention, the method for performing temper rolling includes performing wet temper rolling on an annealed cold rolled steel sheet, and the method includes setting the tension T (kgf/mm²) for the temper rolling based on the carbon content C (mass%) of the cold rolled steel sheet. Furthermore, the tension T may be set based on the sheet thickness t (mm) of the cold rolled steel sheet, the load w (tonf/mm) per unit width, and the surface roughness a (µmRa) of a work roll, in addition to the carbon content C (mass%). More preferably, the tension T may be set based on formula (1) below.
$\begin{array}{l} t \times w \times (- 200 \times a - 90) / (a \times (1 - logC)) + 17.1 \leq T \leq t \\ \times w \times (- 200 \times a + 10) / (a \times (1 - logC)) + 17.1 \end{array}$
In formula (1), t is a sheet thickness (mm) of the steel sheet, w is a load (tonf/mm) per unit width, a is a surface roughness (µmRa) of a work roll, C is a carbon content (mass%) of the steel sheet, and T is a tension (kgf/mm²) per unit cross-sectional area. Furthermore, the logarithm in the formula is a natural logarithm.
Formula (1), shown above, is the result derived by, for example, performing multiple regression analysis on data organized from numerous experimental examples and simulated calculation results. It was discovered that in instances where the lower limit and the upper limit of the tension T that satisfy formula (1) are determined, and temper rolling is performed with a tension T set to be within the range, an excellent steel sheet, in which the occurrence of jumping and other problems is prevented, can be obtained.
A review of the relationship between each of the factors and the tension T in formula (1) suggests that the sheet thickness t and the load w are negatively correlated with the tension T. It is apparent that as t and w increase, the value of the tension T at which jumping occurs decreases. On the other hand, the surface roughness a of a work roll and the carbon content C are positively correlated with the tension T. Thus, it is apparent that as a and C increase, the value of the tension T at which jumping occurs increases.
The following description describes the tension T of the present invention, the factors (C, t, w, a) for the tension setting, and parameters and the like associated with the operational conditions of the temper rolling. Note that cold rolled steel sheets of interest in the present invention are automotive steel sheets, steel sheets for cans, and other common cold rolled steel sheets.

Tension T

The tension T of the present invention is within a range of 5.0 kgf/mm² to 30.0 kgf/mm². If the tension T falls outside of the range, sufficient temper rolling cannot be carried out, which leads to the occurrence of problems such as jumping and a shape defect. Preferably, the tension T is within a range of 2.0 kgf/mm² to 16.0 kgf/mm².
The tension T, which is set based on the various factors for the temper rolling, is imparted by adjusting a rotational speed of the work rolls 1, as stated above.

Carbon Content C

A carbon content C (mass%) of the cold rolled steel sheet is an element that serves as a factor that significantly affects the tension T. The carbon content C of the cold rolled steel sheet of the present invention is preferably 0.0005 mass% or more and 0.1 mass% or less. More preferably, the carbon content is 0.001 mass% or more and 0.08 mass% or less.
An analysis of the carbon content C can be performed in accordance with JIS G 1211-3.

Sheet Thickness t

A sheet thickness t (mm) of the cold rolled steel sheet of interest in the present invention is preferably 0.1 mm or more and 1.0 mm or less. More preferably, the sheet thickness t (mm) is 0.1 mm or more and 0.6 mm or less.
A measurement of the sheet thickness t can be performed with a y-ray thickness gauge, an x-ray thickness gauge, or the like.

Load w

The load w (tonf/mm) per unit width is preferably 0.1 tonf/mm or more and 1.5 tonf/mm or less. If the load w (tonf/mm) per unit width falls outside of the range, sufficient temper rolling cannot be carried out, which may lead to the occurrence of problems such as jumping and a shape defect. More preferably, the load w (tonf/mm) per unit width is 0.2 tonf/mm or more and 1.0 tonf/mm or less.
A measurement of the load w can be performed with a load cell or the like.

Surface Roughness a

A surface roughness a (µmRa) of a work roll is preferably 0.20 µmRa or more and 2.00 µmRa or less. More preferably, the surface roughness a (µmRa) is 0.25 µmRa or more and 1.80 µmRa or less.
Note that Ra is one of the parameters representing surface roughness and is a parameter indicating an arithmetic mean roughness. The surface roughness of work rolls can be measured in accordance with JIS B 0601.
An adjustment of the surface roughness of work rolls can be performed by electrical discharge machining, abrasive wheel polishing, or the like.

Annealing Conditions

An annealing step, which is a step preceding the temper rolling step of the present invention, will be described.
A typical annealing step for cold rolled steel sheets uses a continuous annealing line in which an annealing furnace for performing annealing is provided upstream of a temper rolling mill for performing temper rolling. The continuous annealing line includes multiple payout reels for paying out a coil (steel strip) of a cold rolled steel sheet, a welding device, a cleaning device, an annealing furnace, a temper rolling equipment, and multiple reels for coiling the steel sheet.
The payout reels pay out a steel sheet from a steel strip wound as a coil. The steel sheet is drawn from the payout reels and transferred in a longitudinal direction.
In an instance where, for example, there are two payout reels, when payout from one of the payout reels is completed, payout from the other of the payout reels is started, and a trailing end of the preceding steel sheet and a leading end of the succeeding steel sheet are welded together with a welding device; accordingly, the processing of steel sheets is carried out continuously.
Note that having multiple payout reels is not necessarily a requirement, that is, the steel sheet may be paid out from a single payout reel.
The welding device is used to weld together the trailing end of the steel sheet paid out earlier and the leading end of the steel sheet paid out later, thereby integrating the steel sheets together. Accordingly, a steel sheet that is longer than a coil placed on a single payout reel can be processed continuously.
The cleaning device is a device that cleans off and removes oil, dirt, and the like deposited on a surface of the steel sheet. Methods for cleaning the steel sheet by using the cleaning device are not particularly limited, and any of various types of cleaning methods that are used in processing equipment for steel sheets may be employed. Examples of the methods include electrolytic degreasing and alkali degreasing.
The annealing furnace is a device (furnace) for annealing the cleaned steel sheet. The annealing furnace is a typical annealing furnace in which heating, soaking, and cooling are performed.
Preferably, the conditions for the heating process include a temperature of 600°C or more and 850°C or less and a time of 20 seconds or more and 100 seconds or less. More preferably, the temperature is 650°C or more and 800°C or less, and the time is 25 seconds or more and 90 seconds or less.
Preferably, the conditions for the soaking process include a temperature of 600°C or more and 800°C or less and a time of 5 seconds or more and 60 seconds or less. More preferably, the temperature is 650°C or more and 750°C or less, and the time is 10 seconds or more and 55 seconds or less.
Preferably, the conditions for the cooling process include a cooling rate of 5°C/second or more and 30°C/second or less and cooling of the steel sheet to a temperature of 100°C or more and 200°C or less. More preferably, the cooling rate is 10°C/second or more and 25°C/second or less, and the steel sheet is cooled to a temperature of 120°C or more and 180°C or less.

Operational Conditions of Temper Rolling

The temper rolling mill may be a 4-high rolling mill as illustrated in Fig. 1 or may be a 6-high rolling mill or the like. The stand may be a single stand or may be multiple stands which may include wet and dry stands.
Preferably, a work roll diameter ϕ is 450 mm or more and 600 mm or less. In particular, more preferably, the work roll diameter ϕ is 500 mm or more and 550 mm or less.
The temper rolling liquid supply nozzles 5 are provided on a front surface side and a rear surface side of the steel sheet 3 and supply a temper rolling liquid to regions between the steel sheet 3 and the work rolls 1 from an upstream side (entry side) relative to the travel direction of the steel sheet 3. That is, the temper rolling liquid supply nozzles 5 supply a temper rolling liquid to the front surface side and the rear surface side of the steel sheet 3. The supply of a temper rolling liquid to regions between the steel sheet 3 and the work rolls 1 prevents entry of a foreign matter into regions between the work rolls 1 and the steel sheet 3, thereby preventing the occurrence of defects in the steel sheet 3.
Fig. 1 illustrates an instance in which the temper rolling liquid supply nozzles 5 are provided on the entry side, and a temper rolling liquid is supplied to regions between the steel sheet 3 and the work rolls 1; however, the present invention is not limited to this instance. The temper rolling liquid supply nozzles 5 may be provided on a surface of the work rolls 1 or between the work rolls 1 and the back-up rolls 2, and, accordingly, a temper rolling liquid may be supplied. Furthermore, in the instance of a 6-high rolling mill, the temper rolling liquid supply nozzles 5 may be provided between intermediate rolls and the work rolls 1, with the intermediate rolls being provided between the work rolls 1 and the back-up rolls 2, and, accordingly, a temper rolling liquid may be supplied. Furthermore, the temper rolling liquid supply nozzles may be provided not only on the entry side but also on the delivery side.
The type of a temper rolling liquid of the present invention is not particularly limited, and specific examples thereof include surfactants and fatty acids.
Preferably, a supply temperature of the temper rolling liquid is 10°C or greater, and, preferably, the supply temperature is adjusted to be 60°C or less. More preferably, the supply temperature is 20°C or more and 50°C or less.

EXAMPLES

The present invention will now be described in more detail with reference to Examples. The present invention is not limited to these Examples.
A 4-high temper rolling mill as illustrated in Fig. 1 was used. The work roll diameter ϕ was 520 mm. The surface roughness of the work rolls was adjusted by performing polishing with an abrasive wheel. Furthermore, a temper rolling liquid was adjusted to a temperature of 20°C to 40°C and supplied from the entry side of the rolling mill. The temper rolling liquid included a surfactant, fatty acid, and the like.
The steel sheets of interest used were low carbon steel sheets in which the carbon content C was 0.04 mass% and ultra-low carbon steel sheets in which the carbon content C was 0.0014 mass% or 0.0024 mass%.
The sheet thickness t of the steel sheets was 0.2 mm, 0.25 mm, or 0.3 mm. The load w per unit width applied to the steel sheets was 0.3 tonf/mm, 0.5 tonf/mm, or 0.6 tonf/mm. The surface roughness a of the work rolls was adjusted to be 0.28 µmRa, 0.47 µmRa, or 0.88 µmRa.
An operation was performed with the various factors combined, as described above. The actual set tension value was compared with the calculated value determined from the factors, according to formula (1), which is a formula for tension setting as described above. Investigations were made into whether jumping actually occurred and whether a shape defect actually occurred, and the results are shown in Table 1.
Regarding the occurrence of jumping, the determination as to whether jumping occurred was made based on an elongation ratio, which was calculated based on a difference in a peripheral speed between preceding rolls of the temper rolling mill and succeeding rolls thereof. Specifically, in the instance where the elongation ratio was 5% or greater, it was determined that jumping had occurred. Furthermore, regarding the occurrence of a shape defect, the determination as to whether a shape defect occurred was made based on a height of an undulation of the surface of the steel sheet. The height of the undulation of the surface of the steel sheet was measured with a stylus profilometer, and in the instance where a height difference was 0.1 mm or greater, it was determined that a shape occurrence was defective.
Example 1 was carried out as follows. Steel sheets having different carbon contents C were used; the carbon contents C were 0.04 mass%, 0.0024 mass%, and 0.0014 mass%. The other factors were the same for all the steel sheets: the sheet thickness t was 0.2 mm, the load w was 0.3 tonf/mm, and the surface roughness a of the work rolls was 0.28 µmRa. These values were substituted into formula (1) to determine the lower limit and the upper limit of the tension T. In the instances where the tension for the actual operation was set to be within the range of the upper and lower limits (Examples 1-1, 1-5, and 1-8), neither jumping nor shape defects occurred. However, in the instances where the tension was set at a value above the upper limit (Examples 1-2, 1-6, and 1-9), jumping occurred, and in the instances where the tension was set at a value below the lower limit (Examples 1-3, 1-4, and 1-7), a shape defect occurred.
Next, Example 2 was carried out as follows. Steel sheets having different sheet thicknesses t were used; the sheet thicknesses t were 0.2 mm, 0.25 mm, and 0.3 mm. The other factors were the same for all the steel sheets: the carbon content C was 0.04 mass%, the load w was 0.3 tonf/mm, and the surface roughness a of the work rolls was 0.28 µmRa. These values were substituted into formula (1) to determine the lower limit and the upper limit of the tension T. In the instances where the tension for the actual operation was set to be within the range of the upper and lower limits (Examples 2-1, 2-3, and 2-6), neither jumping nor shape defects occurred. However, in the instances where the tension was set at a value above the upper limit (Examples 2-4 and 2-7), jumping occurred, and in the instances where the tension was set at a value below the lower limit (Examples 2-2 and 2-5), a shape defect occurred.
Subsequently, Example 3 was carried out as follows. The load w was set at 0.3 tonf/mm, 0.5 tonf/mm, and 0.6 tonf/mm. The other factors were the same for all the steel sheets: the carbon content C was 0.04 mass%, the sheet thickness t was 0.2 mm, and the surface roughness a of the work rolls was 0.28 µmRa. These values were substituted into formula (1) to determine the lower limit and the upper limit of the tension T. In the instances where the tension for the actual operation was set to be within the range of the upper and lower limits (Examples 3-1, 3-3, and 3-6), neither jumping nor shape defects occurred. However, in the instances where the tension was set at a value above the upper limit (Examples 3-4 and 3-7), jumping occurred, and in the instances where the tension was set at a value below the lower limit (Examples 3-2 and 3-5), a shape defect occurred.
Lastly, Example 4 was carried out as follows. Work rolls having different surface roughnesses a were used; the surface roughnesses a were 0.28 µmRa, 0.47 µmRa, and 0.88 µmRa. The other factors were the same for all the steel sheets: the carbon content C was 0.04 mass%, the sheet thickness t was 0.2 mm, and the load w was 0.3 tonf/mm. These values were substituted into formula (1) to determine the lower limit and the upper limit of the tension T. In the instances where the tension for the actual operation was set to be within the range of the upper and lower limits (Examples 4-1, 4-3, and 4-6), neither jumping nor shape defects occurred. However, in the instances where the tension was set at a value above the upper limit (Examples 4-4 and 4-7), jumping occurred, and in the instances where the tension was set at a value below the lower limit (Examples 4-2 and 4-5), a shape defect occurred.

The above results demonstrated that in the instance where the tension for the actual operation was set to be within the range of the upper and lower limits of the tension determined with formula (1) according to the present invention, favorable temper rolling can be carried out without the occurrence of the problems described above, such as jumping.

[Table 1]

No.	Carbon content C [mass%]	Sheet thickness t of steel sheet [mm]	Load w [tonf/mm]	Surface roughness a of work rolls [µmRa]	Left-hand side of formula (1) (lower limit)	Right-hand side of formula (1) (upper limit)	Tension T of actual operation [kgf/mm²]	Left-hand side of formula (1) (lower limit) satisfied?	Right-hand side of formula (1) (upper limit) satisfied?	Jumping	Shape defect
1-1	0.04	0.2	0.3	0.28	9.7	14.8	12	○	○	None	None
1-2	0.04	0.2	0.3	0.28	9.7	14.8	16	○	×	Occurred	None
1-3	0.04	0.2	0.3	0.28	9.7	14.8	8	×	○	None	Occurred
1-4	0.0024	0.2	0.3	0.28	12.7	15.7	12	×	○	None	Occurred
1-5	0.0024	0.2	0.3	0.28	12.7	15.7	13.0	○	○	None	None
1-6	0.0024	0.2	0.3	0.28	12.7	15.7	16.0	○	×	Occurred	None
1-7	0.0014	0.2	0.3	0.28	13.0	15.8	12	×	○	None	Occurred
1-8	0.0014	0.2	0.3	0.28	13.0	15.8	14	○	○	None	None
1-9	0.0014	0.2	0.3	0.28	13.0	15.8	16.0	○	×	Occurred	None
2-1	0.04	0.2	0.3	0.28	9.7	14.8	12	○	○	None	None
2-2	0.04	0.25	0.3	0.28	7.8	14.2	7	×	○	None	Occurred
2-3	0.04	0.25	0.3	0.28	7.8	14.2	10	○	○	None	None
2-4	0.04	0.25	0.3	0.28	7.8	14.2	15	○	×	Occurred	None
2-5	0.04	0.3	0.3	0.28	6.0	13.6	5	×	○	None	Occurred
2-6	0.04	0.3	0.3	0.28	6.0	13.6	10	○	○	None	None
2-7	0.04	0.3	0.3	0.28	6.0	13.6	14.0	○	×	Occurred	None
3-1	0.04	0.2	0.3	0.28	9.7	14.8	12	○	○	None	None
3-2	0.04	0.2	0.5	0.28	4.7	13.2	4	×	○	None	Occurred
3-3	0.04	0.2	0.5	0.28	4.7	13.2	9	○	○	None	None
3-4	0.04	0.2	0.5	0.28	4.7	13.2	14	○	×	Occurred	None
3-5	0.04	0.2	0.6	0.28	2.3	12.4	2.0	×	○	None	Occurred
3-6	0.04	0.2	0.6	0.28	2.3	12.4	9	○	○	None	None
3-7	0.04	0.2	0.6	0.28	2.3	12.4	13	○	×	Occurred	None
4-1	0.04	0.2	0.3	0.28	9.7	14.8	12	○	○	None	None
4-2	0.04	0.2	0.3	0.47	11.5	14.6	10	×	○	None	Occurred
4-3	0.04	0.2	0.3	0.47	11.5	14.6	12	○	○	None	None
4-4	0.04	0.2	0.3	0.47	11.5	14.6	15.0	○	×	Occurred	None
4-5	0.04	0.2	0.3	0.88	12.8	14.4	12	×	○	None	Occurred
4-6	0.04	0.2	0.3	0.88	12.8	14.4	13.0	○	○	None	None
4-7	0.04	0.2	0.3	0.88	12.8	14.4	15	○	×	Occurred	None

Reference Signs List

1: Work roll
2: Back-up roll
3: Steel sheet
4: Arrow indicating travel direction
5: Temper rolling liquid supply nozzle

Claims

A method for performing temper rolling on a cold rolled steel sheet, the temper rolling including wet temper rolling, the cold rolled steel sheet being an annealed cold rolled steel sheet, the method comprising setting a tension T (kgf/mm²) for the temper rolling based on a carbon content C (mass%) of the cold rolled steel sheet.
The method for performing temper rolling on a cold rolled steel sheet according to Claim 1, wherein the tension T is set based on a sheet thickness t (mm) of the cold rolled steel sheet, a load w (tonf/mm) per unit width, and a surface roughness a (µmRa) of a work roll, in addition to the carbon content C of the cold rolled steel sheet.
The method for performing temper rolling on a cold rolled steel sheet according to Claim 2, wherein the tension T is set based on formula (1) below, $\begin{array}{l} t \times w \times (- 200 \times a - 90) / (a \times (1 - logC)) + 17.1 \leq T \leq t \\ \times w \times (- 200 \times a + 10) / (a \times (1 - logC)) + 17.1 \end{array}$
where t is the sheet thickness (mm) of the steel sheet, w is the load (tonf/mm) per unit width, a is the surface roughness (µmRa) of the work roll, C is the carbon content (mass%) of the steel sheet, and T is the tension (kgf/mm²) per unit cross-sectional area.